1. Field of the Invention
The present invention relates to a communication system and a communication method, in particular, to a communication system and a communication method in which a phone number which is commonly used only among communication terminals of a specific group consisting of members registered in a network is secured and a message can be transmitted/received at an arbitrary point in time.
2. Description of Related Art
Conventionally, only one phone number has been assigned for a communication terminal (or a communication line). Therefore, in a case of communication with a plurality of people, one must know respective phone numbers of communication terminals of all the target destinations and carry out individual communication for each destination even if the communication contents are the same.
As a prior art technique related to this field, numerous patent applications in relation with a sound multiplex system for teleconference have been filed.
In addition, including Magic-Box of NTT (Nippon Telegraph and Telephone Corporation), techniques to execute a function of an answering machine are known to public.
Further, the Internet technology, which a provider relays is also known to public.
By the way, conventionally, it has been necessary to know phone numbers of the communication terminals of all of communication destinations for communicating with a plurality of people, which makes the management of the phone numbers of the communication destinations troublesome.
In addition, it brings a problem that the labor and time required for communication with individual persons become enormous.
Furthermore, in a case where a subscriber of a network possesses and manage a plurality of communication terminals, the subscriber owns a plurality of phone numbers, each number corresponding to each of the plurality of communication terminals, which causes management the phone numbers terrible.
According to the technique of the above-described sound multiplex system for teleconference, all the members should participate in the communication at the same time, and it is not possible for a member to transmit a message to another member and to receive a message from another member to him/her at an arbitrary point time.
In addition, according to the Magic-Box of NTT (Nippon Telegraph and Telephone Corporation), a function of an answering machine of a local line is merely provided externally and the problem of complexity on management due to one-to-one correspondence between a communication terminal (telephone) and a phone number is not solved.
Furthermore, according to the Internet technology, it is necessary to set up a personal computer and to contract with an Internet service provider in addition to have a communication terminal (telephone). Even in a bulletin board function, confidentiality only among the members cannot be always guaranteed.